Brucellosis 2003 proceedings - PHIDIAS

Poster Session
and revaccinated animals and negative group were bacteriological negatives. The
tests used were: Radial Immunodiffusion (RID) and I-ELISA with B. abortus 2308 and
RB51 LPS as capture antigens, and polyclonal antibodies peroxidase conjugates for
anti bovine IgG 1 , IgG 2 , IgM and IgA. For RID, sera from group 4 and infected group
were positives. I-ELISA S-LPS, in vaccinated cows groups 1, 2, 3, the response to
all isotypes was similar to the negative group. In revaccinated cows groups 5 and 6,
IgG 1 response was high. For groups: 4 and infected, positives to RT 1:400 and RID
tests, had a high levels of IgG 2 different with respect to other vaccinated and
revaccinated groups. For I-ELISA R-LPS all groups, included infected cows did not
presented difference in all isotypes with negative cows. We concluded that infected
cows had high IgG 2 levels indicative of a Th1 response. An atypical response in
Brucellosis endemic zones is present after vaccination with RB51. The RID, I-ELISA
S-LPS with IgG 2 and rivanol tests are good possibilities for differentiate vaccinated or
infected cows.
86- PERFORMANCE OF THE Brucella abortus RB51 VACCINE IN HIGH
PREVALENCE HERDS IN MÉXICO.
E. Herrera 1 , E. Díaz-Aparicio 2 , L.Hernández-Andrade 2 , R. Pérez 2 , F.Suárez-Güemes 1 . (1)
Departamento de Microbiología e Inmunología, Facultad de Medicina Veterinaria y Zootecnia,
Universidad Nacional Autónoma de México, México D.F. 04510. México. (2) CENID Microbiología
Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, México.
The Brucella abortus RB51 vaccine was introduced in Mexico in 1998, the
absence of the O antigen do not induce antibodies formation detected by the
standard diagnostic tests. In Mexico the use of this vaccine is recommended in two
different doses, normal dose for calves and reduce dose for pregnant catlle. We
have been monitoring the behavior of the vaccine in areas with high prevalence of
Brucellosis. It was found 94% of protection against natural challenge, the vaccine
strain was isolated from milk and vaginal swabs it was also found a serological
response in the card test but not in Rivanol test. In a prospective study, we follow
1150 vaccinated cows for 660 days, the animals were from two different herds one
with low ( 10%) prevalence (2). In
herd 1 all positive animals were eliminated as well as all the new cases, the
incidence of the disease after one year was 1% by the 2 nd year it was 0%. In herd 2
they eliminated the positive animals by the time of vaccination, but the new cases
were not eliminated, the incidence was higher each month during the 1 st year, time
when they decided to eliminate positive animals and new cases, by the day 540 the
incidence dropped to 1%. Several animals presented a positive reaction to the card
test but were negative again after 2 or 3 months, these animals were negative to
rivanol test. It is important to keep in mind that the positive reaction might be due to
a secondary respond after the animal is exposed to the field strain.
Partially financed by CEE ICA4CT and CONACYT.
138
Brucellosis 2003 International Research Conference